Electrical switch



Patented Mar. 4, 1941 UNITED STATES PATENT OFFlCE smc'r ucu. swrrcn Fred H. Rowe, Gloucester, Mass-.ssslgnor of onefourth to George W. Hooper, Salem, Mass.

Application February-6, 1940, Serial No. m-

2 Claims. v(o1. zoo-a) My present invention relates to switches and more particularly to mercury switches operating on a centrifugal principle whereby the rotation of the switch element causes an electrical circult to be opened or closed, as the case may be.

contact element is centrifugally forced away from the contact member-sand held against return or further agitation while the apparatus is in high rotational speed, and Other objects and novel features comprising the construction and operation of my invention will be apparent as the description of the same progresses.

In the drawing illustrating the preferred embodiment of my invention:

Fig. 1 is a side elevation of the apparatus, as viewed apart from connecting apparatus;

Fig. 2 is a cross-section taken on the line 2-2 of Fig. 1 showing the internal details and also showing a simple electrical diagram with connections to the contact ends of the appara tus as used in actual assembly;

Fig. 3 is a' cross-section taken on the line 3-3 of Fig. 2, and I On the bottom of the casing I0, I have in:

serted an insulated member l3 withn which I have provided a bushing II, the outer end of which is provided with threads for the purpose to of receiving a male member. I

Passing'through the bushing I4, I have shown a shaft l5. Passing down through the bushing II I have shown another shaft It. The opposed ends of the shafts l5 and I! are imbedded in an insulated member ll. Separating the two op- Fig. 4 is a side elevation of the'rotator eleposed ends of the shafts It and I6 is an insulating medium, such as mica or the equivalent,

as indicated in elevation at |8..

The rotor I1, is preferably made from moulded material and is provided with spiral recesses l9 5 and 2|], the top being sealed by means of a cover member 2|. This cover member may be held inplace, 'sealed, or otherwise secured in any suitable manner.

The recesses I! and 20 in the rotor comprise spiral tracts, shown at 2' and I3 respectively. As viewed in Fig. 4, the vertical lines I! and 20 show the deep end of the recesses l9 and 20 with respect to'their' back vertical sides. The recesses terminate-at the surface of the rotor ll under the cover 2|. The numerals- 22 and 23 indicate the spiral bottom surface of these recesses.

At the lowermost portion of the tracts, or bottom surfaces of the recesses, a passage is'provided directly to the insulated shafts l8 and I, such that an area of the shaft ends is bared on either side connecting with the recesses in the rotor.

'In the recesses, I have deposited a certain amount of mercury which forms a rolling flexible ball, as indicatd at 24 and 25.

a At 28, I have indicated the rear stop light of a motor vehicle. 21 indicates the cable leading to a speedometer of said motor vehicle. 28 indicates the cable leading to the transmission or other positive elements, of the motor vehicle which control the traction elements of said vehicle,

At 28, I have indicated a battery, one of which electrical poles connects with a common ground At 3|, I have shown a simple switch, preferably mounted on the control panel of an automobile.

In operation. assuming that the switch involving the present invention is associated with the stop light of'an automobile, and the panel switch 3| has been closed for evening driving,

. the cable drive from the transmission of the vehlcle or from other parts, as the wheels, rotate.

the shaft it. As the rotor. l1 speeds up, the

- centrifugal force 'throws the mercury members 24 and 2B outward in the tracts l2 and 23. The mercury balls roll up the inclined tracks 22 and 23 to the highest point and remain there while the rotor I1 is revolving at high speed. When the vehicle slows down and the rotor H decreases its' speed to a predetermined degree, the

-mercury balls 24 and 2! return by means of gravity and contact the two opposed ends of the shafts I! and "I8 bridging the insulating material I8 which separates the shaft ends. In this position, and assuming that the dash switch Ii is in a closed position, the circuit through the tail light lamp is completed and the tail light is illuminated.

When my switch is applied to the tail light of a motor vehicle it will be apparent that when the vehicle .is traveling at normal speed on a highway, the stop light will not be illuminated but in the event that the driver slows up to make a stop or to make a turn, the tail light will become illuminated regardless of whether or not the driver has used his foot or emergency brake.

A very important element oi! my invention lies in the inclined tracks 23 and 22 because it is necessary that the mercury balls 24 and 25 remain fixed at the upper ends of such tracks with respect to the tracks themselves. that the mercury is prevented from becoming broken up into-a multiplicity of small balls as is the case where a cup shaped cavity is used. Such a break up of the mercury in a cup shaped recess is due to the fact that the surface of a -cup races around under the mercury more or less without rotating the mercury with it. These fine By this I mean particles of mercury having a much lesser weight settle back and close the circuit between the two shafts or other contacts defeating the purpose of the device.

Having thus described my invention what I of said track terminating at the insulated ends oi? said shafts, a ball of mercury located in said recess and rolling on said track, a casing supporting said rotor and journals for said rotor to revolve on.

2. In an electrical centrifugally operated mercury switch, an insulated rotor having ashaft at either end journalled in a casing, the opposed ends of said shafts located with said rotor being insulated from each other, an internal closed recess in said rotor having a bottom track comprising a spiral groove, the lower end of said track engaging with the exposed ends of said shafts, a mercury ball located in said recess.

FRED H. ROWE. 

